It is increasingly common for both below-grade and above-grade concrete walls to be constructed using insulated concrete formwork (or “ICF”) systems. In conventional concrete wall-forming systems, a pair of wood or metal form panels are set up at a spacing corresponding to the desired thickness of the finished wall, thus creating a cavity between the panels. As necessary or desired, steel reinforcing bars are positioned within the formwork cavity. The form panels are secured in position using form ties extending between the form panels, and/or by means of external temporary bracing. Fluid concrete is then introduced into the formwork cavity. After the concrete has cured sufficiently, the formwork panels are removed (or “stripped”) from the concrete wall.
It is generally desirable to in insulate both above-grade and below-grade building walls, in order to minimize through-wall heat transfer both from inside the building to the outside (e.g., during winter) and from the outside into the building (e.g., during summer). By minimizing heat transfer, wall insulation reduces heating costs in cold weather, and reduces air conditioning costs in warm weather (or enhances the comfort of persons in buildings that do not have air conditioning). For concrete walls constructed using conventional methods, insulation is typically applied to one or both wall surfaces, such as in the form of plastic foam insulation panels glued or otherwise attached to the concrete surface, or (particularly in the case of inside wall surfaces) in the form of fiberglass batts incorporated into stud walls or strapping systems installed adjacent to the wall surface. These conventional wall insulation methods and systems add to the total time and cost of building construction.
ICF systems combine plastic foam insulation panels and spacing means (such as plastic the members) to create assemblies in which the insulation panels take the place of conventional wall form panels (e.g., plywood forms), and remain in place as permanent insulation after the concrete wall has been cast and cured. ICF systems thus reduce or eliminate the need to strip forms from the finished wall, thereby reducing construction labour costs. As well, construction time and costs are further reduced because wall insulation does not have to be installed as a separate task subsequent to wall construction.
It is commonly necessary or desirable for floor (or roof) beams and joists to act as struts providing effective lateral bracing to the walls that support them. In some cases, such bracing action may be structurally required on a long-term basis; in other (and perhaps most) cases, the beams and joists may need to provide bracing only until the complete floor (or roof) structure is in place. This bracing effectiveness is easily achieved in conventional concrete wall construction by embedding the supported ends of the beams and joists into the walls as the walls are being cast, thus providing solid support for the beams and joists both vertically and laterally. However, it is somewhat difficult to embed beams and joists in concrete walls formed using ICF systems. This would typically require cutting out sections of insulation to accommodate the beams and joists, and in some cases temporary shoring may be needed because the ICF panels may not be strong enough to support the weight of the embedded beams and joists during wall construction.
For these reasons, a variety of joist and beam hanger designs have been developed for use with ICF systems. One known ICF joist hanger system, the ICF-Connector™ made by ICF-CONNECT Ltd. of Woodbridge, Ontario, uses a pair of flat metal side plates that are inserted partway through corresponding and suitably spaced vertical slots in an ICF form panel, such that an inner portion of each plate will be east into the concrete wall and an outer portion will protrude from the outer face of the form panel. After the concrete wall has been cast, a U-shaped metal bracket is positioned under the end of the joist to be supported. The joist end is then positioned between the protruding side plates, and suitable fasteners (e.g., sheet metal screws) are installed to connect both side plates to the vertical legs of the U-shaped bracket. Because the side plates are rigidly anchored in the concrete wall, their connection to the bracket allows the hanger assembly to transfer loads both vertically and laterally between the joist and the concrete wall (subject to proper structural design of the hanger components and fasteners).
However, all load transfer in such hanger systems is by way of shear across the fasteners. If the fasteners are corroded, insufficiently tight, or installed in oversized holes, the hanger assembly's bi-directional load transfer capability can be seriously compromised. Accordingly, there is a need for an ICF joist hanger that provides secure bi-directional load transfer capability without relying on shear-loaded fasteners, and without requiring extensive cutouts in the ICF form panels. Moreover, there is at need for such an ICF hanger of unitary or one-piece construction, to minimize hanger fabrication costs. The present invention is directed to these needs.